Gaussian beams are well understood frequency- domain entities combining the directional properties of plane waves with an effectively finite region of support. These outstanding properties are retained not only on a prescribed observation plane, but throughout the propagation path. A preprocessing sequence aimed at transforming raw seismic data into beam stacks is proposed. That is, time-harmonic Gaussian beams are synthesized, replacing the plane waves generated by conventional slant-stacking procedures.

The suggested scheme is characterized by an open parameter, essentially the beam width, whose selection is critical to ultimate success. Specific criteria for choosing this parameter can be given. In the limits of zero and infinite beam widths, beam stacks degenerate to the original raw data and to the conventional slant stacks, respectively.

Although beam stacking is basically a frequency-domain procedure, a transformation into the time domain, using frequency constituents within selected bands, may be accomplished without losing finite spatial support. Advantages of choosing beam-stacked data as a starting point for subsequent inversion may be cited on two levels. The intrinsic property of finite spatial support overcomes edge effects. In addition, the degree of localization achieved by beam stacking may point the way to new approaches to seismic imaging.

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